Alloy for die-cast vehicle parts and method for manufacturing the same

ABSTRACT

An alloy for die-cast vehicle parts and a method for manufacturing the alloy are provided. The alloy includes aluminum as a main component; magnesium in an amount of about 8.0 to 10.5 wt % based on the total weight of the alloy composition; silicon in an amount of about 1.9 to 3.4 wt % based on the total weight of the alloy composition; copper in an amount of about 0.4 to 2.0 wt % based on the total weight of the alloy composition; manganese in an amount of about 0.3 to 1.0 wt % based on the total weight of the alloy composition; beryllium (Be) at a maximum of about 50 ppm, and other essential impurities. Further, during the manufacturing process, a molten metal is heated to a temperature of about 670 to 730° C. and is injected into a die at a speed of about 3.0 m/s or greater.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2014-0138797, filed Oct. 15, 2014, the entire contents of which is incorporated herein for all purposes by this reference.

TECHNICAL FIELD

The present invention relates to an alloy for die-cast vehicle parts and a method for manufacturing the alloy. Accordingly, a high corrosion resistant light aluminum alloy may be manufactured and applied to the die-cast vehicle parts.

BACKGROUND

Typically, an ADC10/12 alloy used for die-cast vehicle parts costs less and has excellent castability, and thus, it has been widely used. As a driving environment of a vehicle becomes more severe, the ADC10/12 alloy has gradually shown limitations. For example, damage may be caused by a lack of durability, a white rust may occur due to salinity of sea water or a snow removal material, and the like, which have not been addressed in the vehicle parts until recently. Therefore, a necessity of a new alloy for supplementing the ADC 10/12 alloy has emerged.

Moreover, environmental regulations have recently been strengthened to make efforts to suppress environmental pollution, and therefore, the environmental regulations have become stricter. Accordingly, vehicle industries have continuously conducted research to reduce a weight of vehicle parts to improve fuel efficiency, but have still had difficulty in determining an alternative alloy having essential performance and price competitiveness that can replace the currently used commercial alloys.

The contents described as the related art have been provided only for assisting in the understanding for the background of the present invention and should not be considered as corresponding to the related art known to those skilled in the art.

SUMMARY

Thus, in preferred aspects, the present invention provides an alloy for die-cast vehicle parts and a method for manufacturing the vehicle parts that are capable of increasing durability greater than about 40% compared to those manufactured from the conventional alloy. In addition, white rust appearing in various aluminum parts may be prevented. When the new aluminum alloy having improved strength and corrosion resistant is applied to the die-case vehicle part, weight thereof may be reduced by about 7% for the same shape by reducing a density of the alloy. Accordingly, weight and cost of aluminum die-cast vehicle parts may be reduced and durability of the aluminum die-cast vehicle parts may be improved.

According to an exemplary embodiment of the present invention, provided is an alloy for die-cast vehicle parts. The alloy may include: aluminum (Al) as a main component; magnesium (Mg) in an amount of about 8.0 to 10.5 wt % based on the total weight of the alloy composition; silicon (Si) in an amount of about 1.9 to 3.4 wt % based on the total weight of the alloy composition; copper (Cu) in an amount of about 0.4 to 2.0 wt % based on the total weight of the alloy composition; manganese (Mn) in an amount of about 0.3 to 1.0 wt % based on the total weight of the alloy composition; beryllium (Be) at a maximum of about 50 ppm; and other essential impurities. In particular, a weight ratio of Mg to Si (Mg/Si) ranges from about 3.1 to about 4.3.

A generation amount of Al—Mg—Cu-based intermetallic compound may be equal to or greater than about 7.0%. A tensile strength may be equal to or greater than about 300 MPa and a yield strength may be equal to or greater than about 170 MPa. The Al—Mg—Cu-based intermetallic compound, as a main strengthening phase, may be dispersedly distributed in an aluminum matrix, together with Mg₂Si particles. A size of the Mg₂Si particle may be in a range from about 10 to about 30 pm.

It is also provided that the alloy of the invention may consist of, or consist essentially of the above-mentioned components in its composition. For example, the alloy for die-cast vehicle parts as described herein may consist or consist essentially of: aluminum (Al) as a main component; magnesium (Mg) in an amount of about 8.0 to 10.5 wt % based on the total weight of the alloy composition; silicon (Si) in an amount of about 1.9 to 3.4 wt % based on the total weight of the alloy composition; copper (Cu) in an amount of about 0.4 to 2.0 wt % based on the total weight of the alloy composition; manganese (Mn) in an amount of about 0.3 to 1.0 wt % based on the total weight of the alloy composition; beryllium (Be) at a maximum of about 50 ppm.

According to another exemplary embodiment of the present invention, provided is a method for manufacturing an alloy for die-cast vehicle parts. In particular, the alloy may include: aluminum (Al) as a main component; magnesium (Mg) in an amount of about 8.0 to 10.5 wt % based on the total weight of the alloy composition; silicon (Si) in an amount of about 1.9 to 3.4 wt % based on the total weight of the alloy composition; copper (Cu) in an amount of about 0.4 to 2.0 wt % based on the total weight of the alloy composition; manganese (Mn) in an amount of about 0.3 to 1.0 wt % based on the total weight of the alloy composition; beryllium (Be) at a maximum of about 50 ppm; and other essential impurities. Further, a molten metal in which a weight ratio of Mg to Si (Mg/Si) may range from about 3.1 to about 4.3 may be heated to a temperature of about 670 to 730° C. The molten metal may be injected into a die at a speed of about 3.0 m/s or greater.

Further provided are die-cast vehicle parts that may comprise the alloy having composition as described herein.

Other detailed matters of the present invention are included in the detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 shows a photograph that includes exemplary micro structures from an exemplary embodiment of the present invention and from the related art;

FIG. 2 illustrates exemplary parts where a hot crack occurs due to a high injection velocity; and

FIG. 3 shows exemplary fluidity evaluation results depending on a melt temperature.

DETAILED DESCRIPTION

It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.

The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about.”

Hereinafter, an alloy for die-cast vehicle parts and a method for manufacturing the same according to various exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

An alloy for die-cast vehicle parts according to an exemplary embodiment of the present invention may include aluminum (Al) as a main component to implement reduced weight, improved strength, and improved corrosion resistant properties compared to the current alloy for die-cast vehicle parts. The alloy for die-cast vehicle parts may further include: magnesium (Mg) in an amount of about 8.0 to 10.5 wt % based on the total weight of the alloy composition; silicon (Si) in an amount of about 1.9 to 3.4 wt % based on the total weight of the alloy composition; copper (Cu) in an amount of about 0.4 to 2.0 wt % based on the total weight of the alloy composition; manganese (Mn) in an amount of about 0.3 to 1.0 wt % based on the total weight of the alloy composition; beryllium (Be) at a maximum of about 50 ppm; and other essential impurities. In particular, a weight ratio of Mg to Si (Mg/Si) may be in a range from about 3.1 to about 4.3 for generation and appropriate distribution of Al—Mg—Cu-based intermetallic compound thereby improving strength and corrosion resistance.

Further, the generation of the intermetallic compound may be suppressed by adding Mg, Si, and Cu during various researches and experiments. For example, the Mg/Si ratio may be set to about 1.98 to 2.5 to obtain a micro structure, and then ultrasonic treatment and the like may be performed, thereby obtaining an alloy having a pseudo-binary system process structure of Al—Mg₂Si. However, as contents of the alloy are increased, the process conditions which may obtain the targeted pseudo-binary system process structure of the alloy may be limited, and therefore, may have a problem such that a quality deviation may increase.

Therefore, according to the exemplary embodiment of the present invention, the Mg/Si ratio may be increased to implement a complex micro structure in which a substantial amount of Al—Mg—Cu-based intermetallic compound and primary crystal Mg₂Si are generated, thereby providing improved strength, reduced density, improved corrosion resistant alloy compared to the conventional alloy during a general casting process.

FIG. 1 shows a photograph that includes an exemplary micro structure of an exemplary alloy prepared according to an exemplary embodiment of the present invention and a photograph of an exemplary pseudo-binary system process structure according to the related art. As shown in FIG. 1, compared to the micro structure with the pseudo-binary system process structure in which eutectic Mg₂Si particles are finely distributed in a typical aluminum matrix (Al matrix), the alloy according to the exemplary embodiment of the present invention may include the Al—Mg—Cu-based (white) intermetallic compound. In particular, the Al—Mg—Cu-based (white) intermetallic compound may be a major strengthening phase, uniformly distributed therein. Further, the exemplary alloy may include the primary crystal Mg₂Si particles (black) having a size in a range from about 10 to about 30 μm distributed therein.

When the size of the Mg₂Si particle is greater than about 30 μm, an alloy of the present invention may not be prepared to have a sufficient tensile strength of about 300 MPa and a sufficient yield strength of about 170 MPa or greater as used for the die-case vehicle parts. When the size of the Mg₂Si particle is less than about 10 μm, the alloy may have a structure similar to the pseudo-binary system process structure in the related art as shown in FIG. 1. Particularly, the alloy of the present invention may be differentiated from the conventional alloys by reducing a ratio of other alloy elements except Mg and increasing a micro structure mainly based on a primary crystal aluminum resin, thereby maximizing elongation.

Hereinafter, the reason for limiting a numerical value of a composition of the alloy for die-cast vehicle parts according to the exemplary embodiment of the present invention will be described.

Magnesium (Mg), as used herein, may be one of the most important element that implements improved strength, improved corrosion resistant, and reduced density properties. The amount of Mg may be of about 8.0 to 10.5 wt %. When the Mg is added less than about 8.0 wt %, an amount of Al—Mg—Cu-based intermetallic compound may be insufficiently generated and thus a desired amount of Al—Mg—Cu-based intermetallic compound when adding Si may not be obtained. Accordingly, the amount of intermetallic compound which implements the improved strength, improved corrosion resistant properties may be reduced and thus the desired physical properties may not be obtained. When the Mg is added in an amount greater than about 10.5 wt %, coarsening and generation of hot crack of the Al—Mg—Cu-based intermetallic compound may occur and thus castability and mechanical physical properties may deteriorate.

Silicon (Si), as used herein, may be a component to improve the castability of the alloy and an amount of Si may be of about 1.9 to 3.4 wt %. When the Si is added in an amount less than about 1.9%, castability may not be improved sufficiently, and when the Si is added in an amount greater than about 3.4%, a substantial amount of Mg₂Si particles may be generated instead of the Al—Mg—Cu-based intermetallic compound which is a main strengthening particle, and thus, corrosion resistance and the strength may be reduced.

Further, to obtain substantially improved strength and corrosion resistant properties, the weight ratio of Mg to Si (Mg/Si) may be adjusted within a range of about 3.1 to 4.3. When the ratio of Mg/Si is less than about 3.1, a size of Si may be coarsened. When the ratio of Mg/Si is greater than about 4.3, the Mg₂Si particle may not be generated.

Copper (Cu), as used herein, may form the Al—Mg—Cu-based intermetallic compound as of a strengthening phase together with the Mg. When the Cu is added in an amount less than about 0.4%, the strengthening effect may not be sufficient, and when the Cu is added in an amount greater than about 2.0%, an intermetallic compound which causes galvanic corrosion from the Al matrix may be generated and thus the corrosion resistance may be reduced.

Manganese (Mn), as used herein, may be added to reduce a die soldering problem that may occur during the die casting. When the Mn is added in an amount less than about 0.3%, the soldering reducing effect may be insufficient, and when the Mn is added in an amount greater than about 1%, an intermetallic compound having a coarse bar shape may be generated and thus strength may be reduced.

Beryllium (Be), as used herein, may be a finite element to prevent generation of oxide inclusion in a product by suppressing surface oxidation when melting the alloy including a substantial amount of Mg. The Be may be added at a maximum of about 50 ppm according to the die casting process conditions.

A method for manufacturing an alloy for die-cast vehicle parts is also provided according to an exemplary embodiment of the present invention. The alloy for die-cast vehicle parts may have the composition as described above. Accordingly, a filling defect problem due to the reduction in castability which may occur when preparing the alloy (ADC10/12) which is used for the typical die casting product and the casting defect problem due to the occurrence of hot cracks and the shrinkage cavity may be prevented. In particular, the method for manufacturing an alloy for die-cast vehicle parts according to the exemplary embodiment of the present invention may apply casting process conditions such as molten metal temperature, injection velocity, cooling time, and the like, and such process conditions may be differentiated from the conventional die casting process conditions to prevent the hot crack, the non-filling, the shrinkage defect, and the like, thereby providing mass production. As a result, such problems, for example, lack of durability and the white rust, which are caused during the conventional die-cast parts, may be prevented and weight reduction effect may be obtained.

In an exemplary method for manufacturing an alloy for die-cast vehicle parts, the molten metal temperature may be elevated to a temperature at least of about 670° C. or greater since reduced fluidity compared to the ADC10/12 alloy. Further, since a content of Mg is relatively greater than that of other elements, the molten metal temperature may be limited to a temperature at maximum of about 730° C. to prevent a molten metal oxidation problem.

Further, since the alloy according to the exemplary embodiment of the present invention may have a greater mushy zone than that of the ADC10/12 alloy, a filling time may be reduced. Accordingly, the high injection velocity may be at least of about 3.0 m/s or greater and a switching position may be limited to a maximum of 8/10 point of a sleeve length. As shown in Table 1, the generated amount of the Al—Mg—Cu-based intermetallic compound in each example is shown as the content of Mg in each example varies. In addition, effects of the generation amount of the Al—Mg—Cu-based intermetallic compound on improving strength and corrosion resistant properties in the Al—Mg—Si-based alloy are compared.

TABLE 1 Generation amount of Mg Si Al-Mg-Cu-based intermetallic Division Al (wt %) (wt %) compound (%) Comparative Balance 7.5 3.0 4.0 Example 1 Comparative Balance 8.0 3.0 5.0 Example 2 Example 1 Balance 8.5 3.0 7.0 Example 2 Balance 9.0 3.0 8.0 Example 3 Balance 9.5 3.0 9.5 Example 4 Balance 10.0 3.0 10.5 Example 5 Balance 10.5 3.0 12.0

As shown in Table 1, sufficient amounts of intermetallic compound are generated when the Mg is added in an amount of about 8.0 wt % or greater. The amount of intermetallic compound is increased in proportion to the content of Mg, but when the Mg is added greater than about 10.5 wt %, the hot crack occurs and thus it is highly likely to increase the defective rate during the casting process.

The mechanical natures of the alloys were tested while changing a content of Cu in an Al-10 Mg-3Si-based alloy to confirm improvement in strength properties of an Al—Mg—Si—Cu-based alloy. The results are shown in the following Table 2.

TABLE 1 Tensile Yield Division Al Mg(wt %) Si(wt %) Cu(wt %) strength(MPa) strength(MPa) Comparative Balance 10 3.0 0.3 280 160 Example 3 Example 6 Balance 10 3.0 0.4 310 175 Example 7 Balance 10 3.0 0.5 325 185 Example 8 Balance 10 3.0 0.7 325 210 Example 9 Balance 10 3.0 0.9 335 220

As shown in Table 2, as the content of Cu is increased, the mechanical properties of the Al—Mg—Si-based alloy are improved.

To obtain the targeted improvement in strength of 300 MPa or greater, it may be appreciated that Cu may be added in an amount greater than about 0.4 wt %. Similar to the Mg, the Cu has the improved mechanical natures in proportion to the increase in the content of Cu, but when the Cu is added in an amount greater than about 2.0 wt %, the corrosion resistance is reduced due to the galvanic corrosion, and thus, the amount of Cu needs to be limited.

FIG. 2 illustrates exemplary die-cast vehicle parts where the hot crack may occur due to the change in the molten metal high injection velocity. As illustrated in FIG. 2, as the result of an experiment, when the same molten metal satisfying the composition of the alloy according to the exemplary embodiment of the present invention is used but the high injection velocity is different, the hot cracks occur, for example, when the high injection velocity is about 2.4, about 2.6, and about 2.8 m/s. Meanwhile, the hot cracks disappear when the high injection velocity is about 3.0 m/s and therefore an improved quality of product may be obtained.

FIG. 3 illustrates the result of an experiment of fluidity evaluation of the molten melt. As the result of an experiment using the same molten metal satisfying the composition of the alloy according to the exemplary embodiment of the present invention, the molten metal may secure the sufficient fluidity at a temperature of about 670° C. or greater.

As described above, according to the alloy for die-cast vehicle parts and the method for manufacturing the same according to the present invention, the durability may be increased by greater than 40% compared to the conventional alloy and the white rust appearing in various aluminum parts may be prevented by developing the die-cast vehicle parts to which the high-strength, high corrosion resistant new aluminum alloy is applied. Further, weight of the parts may be reduced by about 7% in the same shape by reducing the density to reduce the weight, and cost of the aluminum die-cast vehicle parts may be reduced, while the durability of the aluminum die-cast vehicle parts may be improved.

It will be understood by those skilled in the art that the present invention may be practiced in other detailed forms without changing the technical idea or the essential features. Therefore, it should be understood that the above-mentioned embodiments are not restrictive, but are exemplary in all aspects. It should be interpreted that the scope of the present invention is defined by the following claims rather than the above-mentioned detailed description and all modifications or alterations deduced from the meaning, the scope, and equivalences of the claims are included in the scope of the present invention. 

What is claimed is:
 1. An alloy for die-cast vehicle parts, comprising: aluminum (Al) as a main component; magnesium (Mg) in an amount of about 8.0 to 10.5 wt % based on the total weight of the alloy composition; silicon (Si) in an amount of about 1.9 to 3.4 wt % based on the total weight of the alloy composition; copper (Cu) in an amount of about 0.4 to 2.0 wt % based on the total weight of the alloy composition; manganese (Mn) in an amount of about 0.3 to 1.0 wt % based on the total weight of the alloy composition; a maximum of about 50 ppm of beryllium (Be); and other essential impurities, wherein a weight ratio of Mg to Si (Mg/Si) ranges from about 3.1 to about 4.3.
 2. The alloy of claim 1, wherein a generation amount of Al—Mg—Cu-based intermetallic compound is equal to or greater than about 7.0%.
 3. The alloy of claim 1, wherein a tensile strength is equal to or greater than about 300 MPa and a yield strength is equal to or greater than about 170 MPa.
 4. The alloy of claim 1, wherein an Al—Mg—Cu-based intermetallic compound which is a main strengthening phase is dispersedly distributed in an aluminum matrix, along with Mg₂Si particles.
 5. The alloy of claim 4, wherein a size of the Mg₂Si particle is from about 10 to about 30 μm.
 6. The alloy of claim 1, consisting essentially of: aluminum (Al) as a main component; magnesium (Mg) in an amount of about 8.0 to 10.5 wt % based on the total weight of the alloy composition; silicon (Si) in an amount of about 1.9 to 3.4 wt % based on the total weight of the alloy composition; copper (Cu) in an amount of about 0.4 to 2.0 wt % based on the total weight of the alloy composition; manganese (Mn) in an amount of about 0.3 to 1.0 wt % based on the total weight of the alloy composition; and a maximum of about 50 ppm of beryllium (Be).
 7. A method for manufacturing an alloy for die-cast vehicle parts, wherein the alloy comprises: aluminum (Al) as a main component; magnesium (Mg) in an amount of about 8.0 to 10.5 wt % based on the total weight of the alloy composition; silicon (Si) in an amount of about 1.9 to 3.4 wt % based on the total weight of the alloy composition; copper (Cu) in an amount of about 0.4 to 2.0 wt % based on the total weight of the alloy composition; manganese (Mn) in an amount of about 0.3 to 1.0 wt % based on the total weight of the alloy composition; beryllium (Be) at a maximum of about 50 ppm, and other essential impurities, and a molten metal in which Mg/Si ranges from about 3.1 to about 4.3 is heated to a temperature of about 670 to 730° C. and is injected into a die at a speed of about 3.0 m/s or greater.
 8. A die-cast vehicle part that comprises an alloy of claim
 1. 